Java 16 Modularisation IllegalAccessException Java.NIO Spring Boot

Question

I'm new to Java and have been coding in JDK 11, but now using JDK 16. When I try to open a database connection method from the Spring Boot main class, by calling the database connection class, even when it is inside the same package, I get this error:

java.lang.reflect.InaccessibleObjectException: Unable to make public jdk.internal.ref.Cleaner java.nio.DirectByteBuffer.cleaner() accessible: module java.base does not "opens java.nio" to unnamed module

I researched and found JDK 16 may require modular definitions to be able to access classes outside its own class, so I set up a module-info.java file in the package root and added all the requires and exports, but this throws further errors that some classes are not accessible by others, so I have deleted it for now.

I'm reluctant to use this hack in the JVM: https://nipafx.dev/five-command-line-options-hack-java-module-system/

Any advice on how to open a LevelDB connection from an outside class? I am missing something very simple?

EDIT:

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.3</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>org.example</groupId>
    <artifactId>java16-leveldb</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <maven.compiler.source>16</maven.compiler.source>
        <maven.compiler.target>16</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.iq80.leveldb</groupId>
            <artifactId>leveldb-api</artifactId>
            <version>0.9</version>
        </dependency>
        <dependency>
            <groupId>org.iq80.leveldb</groupId>
            <artifactId>leveldb</artifactId>
            <version>0.9</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
</project>

SPRING MAIN CLASS:

package io.strata.node.stratanode;

import io.strata.node.stratanode.database.DatabaseConnection;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class StrataNodeApplication {

    public static void main(String[] args) {
        SpringApplication.run(StrataNodeApplication.class, args);
        DatabaseConnection databaseConnection = new DatabaseConnection();

    }

}

DATABASE CONNECTION CLASS:

package io.strata.node.stratanode.database;

import org.iq80.leveldb.DB;
import org.iq80.leveldb.DBFactory;
import org.iq80.leveldb.Options;
import org.iq80.leveldb.impl.Iq80DBFactory;

import java.io.File;
import java.io.IOException;

public class DatabaseConnection {

    public DatabaseConnection() {
        openDatabaseConnection("test");
    }

    private DB database;
    private DBFactory factory = new Iq80DBFactory();

    public boolean openDatabaseConnection(String filePath) {

        Options options = new Options();
        options.createIfMissing(true);

        try {
            database = factory.open(new File(filePath), options);
            System.out.println(filePath + " has been created");
            return true;

        } catch (IOException e) {
            e.printStackTrace();
        }
        System.out.println(filePath + " database could not be opened/created");
        return false;
    }
}

Answer 1

Turns out that the solution was to upgrade to the latest version of LevelDb which has resolved the issue:

        <dependency>
            <groupId>org.iq80.leveldb</groupId>
            <artifactId>leveldb-api</artifactId>
            <version>0.12</version>
        </dependency>
        <dependency>
            <groupId>org.iq80.leveldb</groupId>
            <artifactId>leveldb</artifactId>
            <version>0.12</version>
        </dependency>
        <dependency>